fixed reference to README_CONFIGURATION.md in README_SETUP.md: reference now ...

fixed reference to README_CONFIGURATION.md in README_SETUP.md: reference now  points to doc/administration/configuration.rst

README_SETUP.md

@@ -118,7 +118,7 @@ server:
       - `INSERT_FILES_IN_DIR_ALLOWED_DIRS`: add mounted filesystems here that
         shall be accessible by CaosDB
     * Maybe set another `SESSION_TIMEOUT_MS`.
-    * See also [CONFIGURATION.md](https://gitlab.indiscale.com/caosdb/src/caosdb-server/-/blob/dev/src/doc/administration/configuration.rst)
+    * See also [CONFIGURATION.rst](https://gitlab.indiscale.com/caosdb/src/caosdb-server/-/blob/dev/src/doc/administration/configuration.rst)
 6. Copy `conf/core/usersources.ini.template` to `conf/ext/usersources.ini`.
     * You can skip this if you do not want to use an external authentication. 
       Local users (CaosDB realm) are always available.